The present invention relates to improvements in plastic reclosable fasteners with sliders particularly suited for thermoplastic bags and the like and particularly to a rolling action zipper profile which closes most easily by pressing it together first at the bottom and then rolling it closed toward the top.
Zippers with sliders are made commercially in several forms. The most common ones uses on clothing have teeth which interlock. The teeth may be made of metal or plastic. Other types of plastic zippers have profiles that include a pair of male and female fastener elements in the form of reclosable interlocking rib and groove elements with the slider for opening or closing the rib and groove elements. In the manufacture of thermoplastic film bags, a pair of these male and female fastener elements extend along the mouth of the bag and these male and female elements are adapted to be secured in any suitable manner to the flexible walls of the thermoplastic film bag. These elements may be integral marginal portions of such walls or they may be extruded separately and thereafter attached to the walls along the mouth of the bag. A method of continuously providing such a fastener on the thermoplastic film is disclosed in U.S. Pat. No. 3,462,332.
The sliders for opening or closing the reclosable fasteners are essentially U-shaped and adapted to be assembled with the fastener or zipper by an endwise assembly or by a relative transverse maneuver. Where the assembly is performed by a relative transverse maneuver, the slider is normally molded from a semi-hard plastic where there is enough yieldability in the side walls of the slider to provide sufficient flexibility to enable spreading apart of the terminal portions of the side walls of the slider so as to clear the interlocking rib and groove elements to permit assembly of the slider with the zipper by relative transverse movement. Where the slider is formed from a metal die-casting or a hard plastic, it has been necessary to rely upon the elastic deformation of the plastic zipper elements to permit the transverse assembly movement of the slider. Such assembly can cause damage to the interlocking rib and groove elements during assembly and leaves something to be desired. Examples of assembly of sliders with plastic reclosable fasteners are disclosed in U.S. Pat. Nos. 3,426,396, 3,660,875, 3,713,923, 3,790,992 and 3,806,998. Flexible plastic zippers of the type having three or more rib and groove continuous interlocking elements thereon are disclosed in U.S. Pat. No. 4,199,845. In this patent, a method is employed wherein the different rib and grooves of each of the tracks are closed progressively one after another so that each one has enough room to interlock before the next one to it is required to respond in the same way. The slider includes an angled bar which successively deforms and interlocks the rib and grooves one after the other from one side to the other side of each of the strips.
Other commercial plastic zippers with sliders have been made by Baron Industries, New York, N.Y., Flexico France, Henonville, France, and some have been imported from Japan by YKK, Lyndhurst, N.J. All of these use a similar profile namely two pairs of hooked shaped elements which are adapted to interlock to hold the zipper closed. The profile is pressed straight together, as is a conventional plastic zipper. When it is opened it is pried straight apart by the separator tab on the slider.